Gullwing advantages

Are gullwings preferrable to other kinds of doors?
When the gullwing is opened, the roof and ceiling rises up as a part of the gullwing. This means that an opened gullwing door should give abundant headroom - it would be easier to reach the seat.
On the other hand, since the opening of the gullwing is a part of the roof, it is allegedly harder to make waterproof...
When the gullwing is opened, the roof and ceiling rises up as a part of the gullwing. This means that an opened gullwing door should give abundant headroom - it would be easier to reach the seat.
On the other hand, since the opening of the gullwing is a part of the roof, it is allegedly harder to make waterproof...